Mean Field Theory of the Square Lattice Antiferromagnetic Heisenberg Model

Abstract

A nearly half-filled two-dimensional Hubbard model has been considered as a model for a high transition temperature oxide superconductor. A new scheme to treat this model, the slave-fermion method, is proposed. The method is applied to the model in the limit of large U at half-filled, where the model reduces to the antiferromagnetic Heisenberg model. It is shown that the ground state energy becomes much lower in the slave-fermion scheme than that in the slave-boson scheme. The ground state shows antiferromagnetic long range order at T =0.